A short statement was issued by the Magpies, and Shearer claims that he was never totally sure as to what exactly Kinnear was employed to do at St James' Park.
He told BBC Sport: "It was a strange appointment in the first place.
"I was surprised that they sold the club's best player (Yohan Cabaye) and they didn't have a plan in place.
"I hope it's not his health, I really do, but I was not sure what his job was in the first place really."
Newcastle were beaten 3-0 by local rivals Sunderland on Saturday.